A malignant pleural effusion was diagnosed by thoracentesis in a 12-year-old patient with an established diagnosis of Wilms' tumor. He was treated with chemotherapy and achieved a reduction in the size of the primary tumor and resolution of the effusion. The primary tumor was then resected and chemotherapy continued for a total of 18 months. At the request of the parents, radiation therapy to the thorax was withheld. The patient has remained free of disease for the past 8 years.